U.S. Pat. No. 4,824,351 discloses a gauging system that employs flowing pressurized gas to sense distances between the elements of a machine and is particularly useful in molding and die casting systems to measure the distances due to the malfunctioning, misalignment and warping of the die elements, and other irregularities in the system. U.S. Pat. No. 4,824,351 discloses molding and gauging systems including, for example, a pair of machine element surfaces, one of which is movable, a source of controlled pressurized air, one or more air outlet orifices in one of the machine element surfaces, fluid lines connecting the source of pressurized air and each of the air outlets, a transducer coupled to each of the fluid lines for monitoring the pressure in each line and providing an output signal indicative of the distance between the machine element surfaces, and a data-processing means coupled to each of the transducers to calibrate the system, to calculate the distance between the machine surfaces, to provide an alarm if the measurements indicate a system irregularity and to provide a permanent record of the measurements. PCT/US88/03561 (published with WIPO No. WO89/03292) discloses improvements of the above system, including more sophisticated data processing and calibration of the system.
The systems described in the above-referenced documents are quite useful in providing information about the operation of machines and the distances of their elements during their operation; however, the measurement from each of the air outlets is somewhat dependent upon the length of the fluid line between the air orifice and the transducer. This presents a problem because, for maximum accuracy, either standard lengths of fluid line must be used during factory calibration and at the customer's location, or calibration must be performed for each of the different lengths of fluid lines used. Since the distances between the pressurized air source and the air outlet orifices can vary widely in applying such systems to operating industrial machinery, a standard line length must be one that is long enough for all possible pressure-source-to-orifice distances, which results in an excessive amount of fluid line cluttering the area about the industrial operation, which can get caught in the machinery and be damaged. If appropriate lengths of line are used to just span the distance between the pressure source and air orifices, then each time a gauging system is moved from one machine to another, the system must be recalibrated over its range of measurement for each different length of hose if maximum accuracy is desired. Thus, it would be highly desirable to have a system that could be calibrated quickly and easily when installed on different machines or used with different molds and dies, and one in which a simple adjustment could be made to account for differing lengths of fluid line that is used.
It would also be desirable to have a valve that provides little restriction to fluid flow and can precisely vary and control fluid flow at high flow rates for use in systems like those described above and others. U.S. Pat. No. 4,673,160 issued to Patrick Tolley, U.S. Pat. No. 4,593,881 issued to Hozo Yoshino and U.S. Pat. No. 4,099,700 issued to Wen Young are typical of various approaches to fluid valves that are intended to provide precise control of flow. Each of these valves either restricts the flow channel considerably, as in U.S. Pat. No. 4,099,700, or forces the fluid to substantially alter its direction of flow, as in U.S. Pat. Nos. 4,673,160 and 4,593,881, both of which also add significant restriction, and possible variability, to the flow in controlling it. It is believed that such valves could not be used in adjusting the gauging systems described above to provide an easily and quickly calibrated system and might introduce variabilities in addition to those resulting from the variable length of fluid line.